You can slacken off the head angle by adding more fork extension, but at the same time you’ll also raise the bottom bracket height. I presume you want to slacken the HA in order to get more stability at speed? Raising the BB may well un-do the benefits of slackening the HA. What bike is it you have and what is it you really want to achieve?

Fit a spacer under the crown race on your fork. Magura sell them. Here’s a Ventana one. I’m sure there are others.

You might have to get the lip machined off though as it probably won’t be compatible with your headset – e.g. the Ventana fits King, and I’m not sure what the Magura is designed for. Or you could get a machine shop to make you one.

thanks for all the information. Bike is a Foes FXR air shock. Running an inch of sag so BB is quite low and HT angle is just over 67 degrees. FOX 36 up front. Wanted to try and slacken to 66.5 to match my old Heckler.

Slackening the head angle by fitting longer forks is a bit risky….
You really need is a bike that’s BUILT with slackness, otherwise you stand a pretty good chance of ruining the handling.
I’ve fallen foul of this before and it can ruin a good bike, beleive me. Yet my Pitch looks slack, it is slack, yet it hadles superbly and climbs pretty decently too….

it’s 20mm per degree – fit a 17mm – 20mm deep lower cup and on a bike you’re well used to you may notice a subtle difference from it slackening 1/4 or so degrees, i’ve done it to a few bikes as a matter of experimentation and left the deeper cup in one as it definately helped, minor mod / fine tune only though. this mod gives you a permanent slacker angle and not a variable one from 10mm extra fork length which is why it’s more noticable than fork extension.

You could try a headset with a larger stack height & then add a ‘hop up’ crown race if required. This would slacken the head angle by a degree or so & lift the headtube as much as 10mm depending on your current headset.

Its also fair to say that the Fox fork isn’t the longest SC fork out there so that could be another option but definately not the cheapest.

Larger front tyre and/or smaller rear would have the same or bigger effect as messing around with headset stack height. Wouldn’t have thought 1/2 deg would make a marked difference to the ride of a fuller susser though and just as easily achieved running more or less sag.